When we think of the most horrific of crops the ones so morally repugnant and -- bear you know the widespread ones that -- -- question humanity. It can help us cope to believe -- happened somewhere else somewhere far away. That's what this weekend's FBI prostitution sting and capture -- over a 150 pimps was so disturbing. Over a hundred children rescue sexual slavery. Here at home. Harris still. And who were the victims. -- BC's -- Denzel went undercover to find. Thanks for cell -- and here in America the businesses sexual slavery but he's looming in the it happens -- thousands of times today on the streets the Internet and those ubiquitous massage -- -- -- strip mall. To understand how this sex business -- We decide to go undercover. And unveiled the secret war. Against. The barrels and Americans. Are willing to pay for sex. It's midafternoon up scientists and -- are in Houston. There's little. But camera that I mean you're -- my somebody damaged my producer poses as a -- constant. When you walk into these places. The first thing you say it's a big window. These girls -- -- confronting you behind the bus. And I guess the idea is that you take your pick number I didn't -- money. -- And good then do. And then -- -- Thank you. Obviously can't disastrous sex. There's a lot of kind of language being news. -- -- -- Time do you think glass windows and steel bars. Women dressed in very revealing clothing. Things that just basically suggest that this isn't your -- massage parlor. Next I -- in myself. I'm -- and journalists working for National Geographic team anyone comes out to talk to me. She's known and. You can't you. Okay they did. -- And many hidden and -- National Geographic. I'm working on a film about ethical content and. As I -- this time. Many signs along the please -- over to his -- I'm Diana the U and that -- can -- -- I don't feel comfortable and good ideas. And that he found I don't know how things work here. I don't mind that he could they have a -- -- -- in order. -- If you can. Proposition. Let me think about it how much would -- thank. OK let me think about it yeah. I am not here. Second friends that I can't arrest him -- he says something that makes me think yeah. He had to get me started on its as a -- He just across the united again brilliant and then like god OK I'm hopeful and it. I don't know streaky house totally crazy -- here's what is it. Pieces this guy until -- -- worked five guys today that it could make thousand dollars today it's pretty good two -- boosters say even if you there. Deal coalition -- how quickly. You can be scooped up dependent war. Later that night we look at amendments. It turns out that he does have a professional. And there is no evidence -- -- -- -- To find out more about that -- -- our next stop is the streets of Charlotte, North Carolina. Tonight we're headed towards a place we've found -- pretty common to have girls walking the streets are concerned this is some of the girls are forced to walk the -- you know against their will. We're out -- Martin and Amy. Two activists from a local Christian. Away -- often hidden population. And American parents Lyme Disease and students extract -- -- Ryan -- we'll track. Mid term used to describe -- CDs street prostitution area is already here. Among prostitutes 75%. Are selling themselves because they are working for a ten. These guys kidnapped. Kill and rape women for a living so that there and they're -- you need to know that going in. Amy -- one younger. This seems especially distraught and defend the -- -- and tell him. The girls erratic behavior. Good indicates that he is -- traffic big time. -- listened and my name's Amy if you ever need anything like clothing anything -- out again. Valuable. Really big thing happened. At the -- campaign. -- yeah. -- -- They're young and maybe. -- -- it okay. They wouldn't teaching. Little -- didn't play. Actually there's a guy coming -- now. I think this prior. As the -- starts to cry we have no idea that this man is -- and I'm just a few feet away. About. You have embraced. Yeah. That has attractive toll. -- you. And there ingesting these girls this -- their boyfriend the other boyfriend's other girlfriend. You're also having a -- street. But it is off the streets that sex traffickers are often hidden in plain -- He had a very very expensive suits. And kept private plane you would never look at him and thank all of this is -- tracker. When -- in -- was nineteen. She started to make a name for herself as a model. Nobody would believe that your sex trafficking that -- I think part of that is just because we've ingrained and ourselves -- -- a sex trafficking victim often is. Jillian grew up as the quintessential girl next door she was a high school -- And -- straight -- students. -- on one modeling job in Arizona. Po -- would change forever. In the middle of the night's three men entered her hotel room one of them was a man in the modeling. And street someone's making her trust. In -- -- quarry to me and a videotaped it and photographed it. When -- returned to -- She was too afraid to go to the police. She decided to put the whole incident behind. And created -- com. And -- that I have all those videos. Of you being raped in Scottsdale. And I'm gonna sell them on the Internet and -- -- -- to them. It became a threat after threat after black -- -- blackmail. And so when he would say hey you know I need you to go to this city or I'm in Charlotte and you meet with this person. Then I did. One of the incredible things about Jillian story is -- a trafficker was a wealthy respected members of the community. It is no standard when he -- for drastic recruits to. They are nearly Ali's master manipulating its. Thank him back makes me sick how many different people about it all the different places and -- body. Is Jessica three years she was -- by pimps the -- Sasha -- all over the country. I mean he had girls in Las Vegas we -- girls and chances we had the girls here in Houston Texas we had present and Oklahoma I mean -- just -- -- from all over the place. What -- they youngest one was thirteen. She looked -- him what happened. I don't know. 2009 the FBI indicted again this -- responsible for trafficking Jessica. I use a piece of property. That's what -- every unit that's wild burros that we're with print that particular guy -- Got branded. You need them pretty. I have a panther on my back and now is there a little logo. And and it's like and have horrible and he can't cover it. So this Lucy show that you belong to -- and their property. -- 2013. Three of the traffickers were sentenced to eight years in prison. I think they sit back. You think that he leopards have time for what he -- -- -- -- -- -- Thousands of times every day that young American Indians are -- insults. Amy not changed alliance right Elaine pulled me enacted streets -- give up that they had nothing to -- them love them unconditionally. -- realized that someone is always waiting couldn't come home. For Nightline I'm -- offense. And Charlotte, North Carolina. Neeson that still happens very -- -- thank you. Inside secret America airs Wednesday -- National Geographic channel. Later this year you be able to see more -- -- -- the joint venture cable channel between ABC news and Univision.

This transcript has been automatically generated and may not be 100% accurate.

Now Playing: Leah Remini on Why She Made Her 'Scientology and the Aftermath' Series

Now Playing: Selena Gomez Is the Queen of Instagram

Now Playing: The Attack: The Heroes of San Bernardino Part 1

Now Playing: {{itm.title}}

{"id":19822448,"title":"Inside the Lives of American Sex Slaves","duration":"3:00","description":"Fusion's Mariana van Zeller investigates U.S. sex trafficking for National Geographic.","url":"/Nightline/video/inside-lives-american-sex-slaves-19822448","section":"Nightline","mediaType":"default"}